dolfin team mailing list archive

[Marie Rognes <meg@xxxxxxxxx>]

Garth Wells wrote:
> Question #109900 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/109900
>
> Garth Wells proposed the following answer:
>
> On 06/05/10 13:52, Marie Rognes wrote:
>   
> > Achim Schroll wrote:
> >     
> > > New question #109900 on DOLFIN:
> > > https://answers.launchpad.net/dolfin/+question/109900
> > >
> > > for a plain Poisson eqn with pure Neumann b.c., how to specify the
> > > scaling condition u*dx = 0 ?
> > >       
> >
> > If you have a recent dolfin, you can introduce a constant c acting as a
> > Lagrange multiplier corresponding to the constraint. See example below.
> >
> >     
>
> Nice. What does 'R' stand for in the definition of the space Q?
>
>   

"Real" (Space of real numbers)


--
Marie

> Garth
>
>   
> > from dolfin import *
> >
> > mesh = UnitSquare(32, 32)
> > V = FunctionSpace(mesh, "CG", 1)
> > Q = FunctionSpace(mesh, "R", 0)
> > M = V * Q
> >
> > (u, c) = TrialFunctions(M)
> > (v, d) = TestFunctions(M)
> >
> > f = Expression("x[0]*x[1]*sin(pi*x[0])")
> >
> > a = dot(grad(v), grad(u))*dx + d*u*dx + c*v*dx
> > L = v*f*dx
> >
> > pde = VariationalProblem(a, L)
> > u_h = pde.solve()
> >
> > plot(u_h[0])
> > interactive()
> >
> >
> > --
> > Marie
> >
> >
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>
>